December 20, 2006

A persistent theme in his work was one practically guaranteed to capture public interest: the possibility that life exists elsewhere in the universe. He became an expert on the subject at a time when it was considered highly speculative, and prodded other scientists to consider it seriously. Civilized life must be common in the universe, he said, because stars are so abundant and the Sun is a fairly typical star.

Dr. Sagan (pronounced SAY-gun) was probably best known as the host of ”Cosmos,” a 13-part series on public television in 1980 that explored everything from the world of the atom to the vastness of the universe, and showed him looking awestruck as he contemplated the heavens. With an audience of 400 million people in 60 countries, it was considered the most widely viewed short-term public television series in history until it was eclipsed in 1990 by a series on the Civil War.

He received critical acclaim as well as substantial financial awards for the series, which made him an international celebrity. The book he wrote to accompany it, also called ”Cosmos,” was on the best-seller list for more than a year, and a company he formed, Carl Sagan Productions, promoted such things as ”The Music of the Cosmos” with RCA Records.

Dr. Sagan was also familiar to television viewers from 26 appearances in the 1970’s and 80’s on ”The Tonight Show” with Johnny Carson, who was known to don a black wig and perform a Sagan impersonation. He and other comics delighted in parodying Dr. Sagan’s references to ”billions and billions” of stars in the universe.

In an interview in 1977, Dr. Sagan said he turned down several hundred requests to give lectures every year but always tried to accept invitations to appear on ”The Tonight Show.”

”The show has an audience of 10 million people,” he said. ”That’s an awful lot of people, and those aren’t people who subscribe to Scientific American.”

Defending his activities in popularizing science, Dr. Sagan said in another interview: ”There are at least two reasons why scientists have an obligation to explain what science is all about. One is naked self-interest. Much of the funding for science comes from the public, and the public has a right to know how their money is being spent. If we scientists increase the public excitement about science, there is a good chance of having more public supporters. The other is that it’s tremendously exciting to communicate your own excitement to others.”

While his leap from the scientific ivory tower into the television studio may have irritated some of his colleagues, there can be no doubt that Dr. Sagan was a serious and productive scientist.